__________ datasets can be added to root dataset to narrow down the search

Child datasets can be added to root datasets to narrow down the search. Datasets are collections of

events that represent your data in a structured and hierarchical way. Datasets can be created by

using commands such as datamodel or pivot. Datasets can have different types, such as events,

search, transaction, etc. Datasets can also have different levels, such as root or child. Root datasets

are base datasets that contain all events from a data model or an index. Child datasets are derived

datasets that contain a subset of events from a parent dataset based on some constraints, such as

search terms, fields, time range, etc. Child datasets can be added to root datasets to narrow down

the search and filter out irrelevant events.